Talaromyces (Penicillium) marneffei is a dimorphic fungus endemic to Southeast Asia that rarely caused disease prior to the human immunodeficiency virus (HIV) era. This fungus can be cultured from the soil but is also commonly cultured from bamboo rats and other commensal rodents.

Presumably, the fungus is inhaled like other dimorphic fungi and then spreads systemically. Primary cutaneous disease has been reported rarely. Vertical transmission to infants from birthing parents with AIDS has been reported rarely. Disseminated disease may occur immediately or during reactivation decades later.

Cutaneous disease is often accompanied by fever, weight loss, hepatosplenomegaly, and lymphadenopathy. In addition to HIV/AIDS (average CD4 count less than 75), other states of immunocompromise have been associated with talaromycosis, including hematologic malignancies, systemic lupus erythematosus, nasopharyngeal carcinoma, renal allografts, solid organ malignancy, and tuberculosis.

Occupational exposure to soil, especially during rainy seasons, has been reported as a risk factor. Northern Thailand is one of the most highly endemic areas, and Thai residents from other parts of the country and travelers from other countries who succumb to talaromycosis usually report travel to this area.